Drag magnet for induction disc type electrical relays and instruments



Apnl 15, 1958 J. w. F. SMITH EI'AL 2,831,165

DRAG MAGNET FOR mnucnou DISC TYPE ELECTRICAL RELAYS AND INSTRUMENTS Filed Oct. 25, 1954 United States Patent DRAG MAGNET FOR INDUCTION DISC TYPE ELECTRICAL RELAYS AND INSTRUMENTS John Walter Freeman Smith and Raymond Harold Bevan Smith, Stafiord, England, assignors to The English Electric Company Limited, London, England, a British company Application October 25, 1954, Serial No. 464,446

Claims priority, application Great Britain November 6, 1953 2 Claims. (Cl. 324-152) This invention relates to braking magnets in electrical relays and instruments which operate on the induction disc principle.

The braking magnet is usually a permanent magnet and the braking effect which it exerts on the induction disc may be controlled by causing the magnet flux which links the disc to change in strength or position relative to the disc. This may be done by adjusting the position of the magnet relative to the disc or by diverting flux along some different path. Another method of adjusting the braking effect which a permanent magnet can exert on an induction disc is that presented by the present invention.

According to the invention, in an electro-responsive device of the induction disc type there is a support structure for supporting a magnetic braking system comprising two magnetic core members at least one of which is a permanent magnet, said support structure comprising a support member for one of the core members pivotally mounted on a support member for the other one of the core members, and there being adjustment means comprising, in combination, a shaft which provides a pivotal connection between the two support members and has its bearing surfaces for one such member eccentrically offset with respect to its bearing surfaces for the other such member so that the relative positions of the members can be adjusted by an angular adjustment of the shaft, and spring bias means seated between one of said support members and two seating surfaces on the other one of said support members, these two seating surfaces being disposed one on either side of the pivotal connection so that the spring bias is operative to take up backlash in the pivotal connection and determine the relative angular attitude of the support members.

According to a feature of the invention, said support structure further comprises clamping means, which are provided between the support members and on one side of the pivotal connection, for use in locking the support members in a relative angular position about the pivotal connection, the magnetic core members being disposed on the other side of this connection.

In the Figs. 1, 2 and 3 of the accompanying drawing, a preferred form of braking magnet according to the invention is depicted.

Fig. 1 shows a preferred magnet structure according to the invention in which the length of air gap in the magnetic circuit can be adjusted. Fig. 2 shows a side elevation of the magnet structure shown in Fig. 1. Fig. 3 shows an elevation of the other side of the magnet structure shown in Fig. 1.

Referring to Figs. 1, 2 and 3, a magnet structure for use in an induction disc type electrical device is shown to comprise a fixed support member 1 and an adjustable support member 2. The support member 1 has two upstanding portions 1a, 1b shown clearly in Figs. 2 and 3. Support member 2 has a tongued portion 3 which fits between the portions 1a and 1b of member 1 and is pivotally mounted near its root by a pivotal connection in the form of a shaft 4a. The position of this shaft is indicated in Figs. 1 and 2. .In the view shown in Fig. 1 only the screw type head of the shaft can be seen whereas in Fig. 2

the shaft itself is indicated by broken lines. The shaft 4a has bearing surfaces which are eccentrically offset with respect to one another. In Fig. 2 the shaft 4a is shown in a position which causes the general level of the bearing surfaces between the shaft and the portion 3 of the member 2 to be higher than that between the shaft and the member 1. It is to be understood that the shaft extends through both portions 1a and 1b of member 1,

the head of the shaft being hidden in theview shown in Fig. 2. A slot is provided in the head of the shaft 4a to enable the angular position ofithe-shaft to be'adjusted' by means of a screw driver. By virtue of the. eccentric offset of the bearing surface between the shaft 4a and the portion 3 of the member 1 it is possible to adjust the displacement between members 1 and 2 by adjusting the angular setting of the shaft 4a. A locking screw 4b threaded into a hole in the upstanding portion 1a of the support member and closely adjacent to the head of the shaft 4a provides a clamping means by which the eccentric adjustment afforded by the shaft 4a can be locked in position The head ofthe screw 4b is able to grip a flange 4a, on the head of the shaft 4a, between the outer surface of portion 1a and a washer 4c carried by the screw 4b.

in order to determine the relative angular positions of the members 1 and 2 about the eccentric pivotal connection provided by the shaft 4a, a strong leaf spring 4d is provided between the members 1 and 2. This leaf spring has a central seating on the underside of a bridge member 1c, which extends between the portions 1a and 1b of the A member 1 and two lower seatings, one for each extremity of the leaf spring. One of the seatings near the end of the tongued portion 3 is remote from the pivotal connection provided by shaft 4a and the other seating is on the other part of the adjustable support member 2 and on the opposite side of the pivotal connection. The leaf spring 4d applies a force on member 2 so as to take up the backlash on the eccentric pivotal connection of shaft 4a. Besides this the spring determines, in conjunction with the magnetic attraction of the system, the angular attitude of member 2 relative to member 1.

In operation, the adjustment of the shaft 4a displaces member 2 bodily from member 1 as the spring 4d ensures a fairly definite angular attitude of member 2 relative-to member 1.

The spring 4d serves the dual purpose of determining this angular attitude and reducing the disturbing eflects caused by small shocks when a device including the braking magnet structure is moved about between, say, testing and circuit positioning operations A screw 5 which passes through a threaded hole in portion 1a of member 1 enables the members 1 and 2 to be clamped in a fixed relative position after an adjustment of the shaft 4a has been made. ables the screw 5 to be locked in setting.

In fixed member 1 is mounted a magnet 6 which is shaped so as to have two poles 7 and 8. A similar magnet 9 is mounted in adjustable member 2. Magnets 6 and 9 are magnetized such that facing poles are of opposite polarity so that the system has a closed magnetic flux path. A change in the distance between the poles of magnets 6 and 9 results from the relative adjustment of members 1 and 2. When the magnet is used in a relay or instrument it is mounted so that the induction disc lies in the air gap between the poles. In Fig. 1 part of an induction disc 10 having a spindle 11 is'shown in position in the gap between the poles of the magnets 6 and 9.

What we claim as our joint invention and desire to secure by Letters Patent is:

1. An electroresponsive device of the induction disc position at any given A lock nut So also en- 3 type wherein there is a support structure for supporting a magnetic braking system comprising two magnetic core members at least one of which is a permanent magnet, said support structure comprising a support member for 013.8 of the core members pivotally mounted on a support member for the other one of the core members, and there being adjustment means comprising, in combination, a shaft which provides a pivotal connection between the two support members and has its bearing surfaces for one such member eccentrically offset with respect to its bearing surfaces for the other such member so that the rqlativepositions of the members can be adjusted by an angular adjustment of the shaft, and spring bias means seated between one of said support members and two seating surfaces on the other one of said support mem- 15 hers, these two seating surfaces being disposed one on either side of the pivotal connection so that the spring bias is operative to take up backlash in the pivotal connection and determine the relative angular attitude of the support members.

2. An electroresponsive device according to claim 1, wherein said support structure further comprises clamping means, which are provided between the support members and on one side of the pivotal connection, for use in locking the support members in a relative angular position about the pivotal connection, the magnetic core mem- 10 bers being disposed on the other side of this connection.

References Cited in the file of this patent UNITED STATES PATENTS 2,284,893 Barnes June 2, 1942 FOREIGN PATENTS 729,370 France July 23, 1932 

